/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: UnionPathExpr.java,v 1.2.4.1 2005/09/12 11:34:14 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import java.util.Vector;

import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;
import com.sun.org.apache.bcel.internal.generic.INVOKESPECIAL;
import com.sun.org.apache.bcel.internal.generic.INVOKEVIRTUAL;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.bcel.internal.generic.NEW;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
import com.sun.org.apache.xml.internal.dtm.Axis;
import com.sun.org.apache.xml.internal.dtm.DTM;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 */
final class UnionPathExpr extends Expression {

  private final Expression _pathExpr;
  private final Expression _rest;
  private boolean _reverse = false;

  // linearization for top level UnionPathExprs
  private Expression[] _components;

  public UnionPathExpr(Expression pathExpr, Expression rest) {
    _pathExpr = pathExpr;
    _rest = rest;
  }

  public void setParser(Parser parser) {
    super.setParser(parser);
    // find all expressions in this Union
    final Vector components = new Vector();
    flatten(components);
    final int size = components.size();
    _components = (Expression[]) components.toArray(new Expression[size]);
    for (int i = 0; i < size; i++) {
      _components[i].setParser(parser);
      _components[i].setParent(this);
      if (_components[i] instanceof Step) {
        final Step step = (Step) _components[i];
        final int axis = step.getAxis();
        final int type = step.getNodeType();
        // Put attribute iterators first
        if ((axis == Axis.ATTRIBUTE) || (type == DTM.ATTRIBUTE_NODE)) {
          _components[i] = _components[0];
          _components[0] = step;
        }
        // Check if the union contains a reverse iterator
        if (Axis.isReverse(axis)) {
          _reverse = true;
        }
      }
    }
    // No need to reverse anything if another expression lies on top of this
    if (getParent() instanceof Expression) {
      _reverse = false;
    }
  }

  public Type typeCheck(SymbolTable stable) throws TypeCheckError {
    final int length = _components.length;
    for (int i = 0; i < length; i++) {
      if (_components[i].typeCheck(stable) != Type.NodeSet) {
        _components[i] = new CastExpr(_components[i], Type.NodeSet);
      }
    }
    return _type = Type.NodeSet;
  }

  public String toString() {
    return "union(" + _pathExpr + ", " + _rest + ')';
  }

  private void flatten(Vector components) {
    components.addElement(_pathExpr);
    if (_rest != null) {
      if (_rest instanceof UnionPathExpr) {
        ((UnionPathExpr) _rest).flatten(components);
      } else {
        components.addElement(_rest);
      }
    }
  }

  public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
    final ConstantPoolGen cpg = classGen.getConstantPool();
    final InstructionList il = methodGen.getInstructionList();

    final int init = cpg.addMethodref(UNION_ITERATOR_CLASS,
        "<init>",
        "(" + DOM_INTF_SIG + ")V");
    final int iter = cpg.addMethodref(UNION_ITERATOR_CLASS,
        ADD_ITERATOR,
        ADD_ITERATOR_SIG);

    // Create the UnionIterator and leave it on the stack
    il.append(new NEW(cpg.addClass(UNION_ITERATOR_CLASS)));
    il.append(DUP);
    il.append(methodGen.loadDOM());
    il.append(new INVOKESPECIAL(init));

    // Add the various iterators to the UnionIterator
    final int length = _components.length;
    for (int i = 0; i < length; i++) {
      _components[i].translate(classGen, methodGen);
      il.append(new INVOKEVIRTUAL(iter));
    }

    // Order the iterator only if strictly needed
    if (_reverse) {
      final int order = cpg.addInterfaceMethodref(DOM_INTF,
          ORDER_ITERATOR,
          ORDER_ITERATOR_SIG);
      il.append(methodGen.loadDOM());
      il.append(SWAP);
      il.append(methodGen.loadContextNode());
      il.append(new INVOKEINTERFACE(order, 3));

    }
  }
}
